The conventional nail coating compositions that have been on the market for many years are organic solvent-based lacquers employing nitrocellulose as the primary film-forming polymeric binder. It has been long recognized in the cosmetics industry that nitrocellulose lacquers fall short of being the ideal nail coating product, primarily due to the harsh organic solvents required both in the formulation of the lacquers and in the subsequent removal of the film from the nails. These organic solvents not only are flammable, malodorous and environmentally undesirable, but also may cause damage to the nails in the course of repeated usage.
In an attempt to avoid the known drawbacks associated with the organic solvent-based nitrocellulose lacquers, a great deal of effort has been expended in recent years toward developing aqueous-based nail coating compositions using in place of nitrocellulose various aqueous emulsion polymeric binders capable upon drying of forming flexible hard films having adhesion to the nail. Representative examples of the aqueous-based nail coating compositions that have previously been proposed are those described in the Greene et al U.S. Pat. No. 4,158,053, issued Jun. 12, 1979, using aqueous emulsion acrylic copolymers, and in the Koch et al U.S. Pat. No. 5,120,529, issued Jun. 9, 1992, using aqueous emulsion polyurethanes and/or polyurethane copolymers such as a polyurethane-acrylate copolymer. The major problem that has been encountered with these prior art aqueous-based formulations is in achieving commercially acceptable coating durability. The binder films formed from these formulations, when compared to nitrocellulose binder films, have been found to have significantly reduced durability in their hardness and adhesion properties, to such a degree that they either wash off or begin to peel off the nail the same day they are applied. Because of a continued lack of success in overcoming this problem, the cosmetics industry has not as yet been able to deliver the long-awaited commercially acceptable aqueous-based alternative to the conventional organic solvent-based nitrocellulose lacquers which, despite their known drawbacks, still remain by default the nail coating product of choice.
Organofunctional hydrolyzable silane coupling agents have been used for many years in various polymer applications for promoting adhesion between an organic polymer and an inorganic substrate like glass, silica, clay, talc, mica, wollastonite, asbestos and metallic surfaces. The silane coupling agents have both an organofunctional moiety selected so as to have reactivity or compatibility with the organic polymer, and hydrolyzable groups which upon hydrolysis form silanol groups having reactivity with surface hydroxyl groups on the inorganic substrate. The adhesion promoting properties of silane coupling agents have previously been used to advantage, for example, in the preparation of inorganic filler-reinforced polymer composites, the immobilization of catalytic enzymes on inorganic supports, the anchoring of polypeptides to inorganic supports in solid phase polypeptide synthesis and analysis, and the coating of ceramic and metallic surfaces with organic polymeric coatings. Use in the formulation of nail coating compositions is not among the previously known applications of silane coupling agents.